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1929. M. L. NELSON ,1,734,94s

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6 Sheets-Sheet 5 M. L. NELSON TESTING APPARATUS Original Filed April 22, 1927 g and Nov. 5, 1929.

1929. x M. L. NELSON 3 48 TESTING APPARATUS Original Filed April 22, 1927 6 Sheets-Sheet 6 Tzsis'hfion 174:; PM? 174/ H45 1m lTaT'iifiLNalsun Patented Nov. 5,1929

UNITED STATES PATENT OFFICE MARTIN L. NELSON, OF PARK RIDGE, ILLINOIS, ASSIGNOR TO RESERVE HOLDING COMPANY, OF KANSAS CITY, MISSOURI, A CORPORATION OF DELAWARE TESTING APPARATUS Application filed April 22, 1927, Serial No. 185,882.

The invention, broadly stated, relates to novel testing equipment for telephone exchanges. More particularly, the invention is concerned with equipment for testing the functions of connector switches used in automatic telephone systems.

The principles involved, and the operations of switches used in automatic telephone systems are well known in the art and will not be discussed in this specification.

However, by way of explaining the term connector it may be stated that this term is generally applied to a switch which has direct access to terminals of subscribers lines. Such a switch is operated in accordance with the last two series of impulses generated at a calling subscribers substation, the series corresponding to the tens and unit digits of the called partys telephone number.

It is imperative to good service thatthe connectors in an exchange be kept in first class condition so that their performance will be accurate and reliable. The best known way of keeping such equipment in reliable order is by routining it, that is, by frequently applying characteristic tests, which, if properly executed indicate that the equipment is functioning properly. A connector has many functions to perform, and, in order to definitely determine that the mechanism and the circuits are performing all their functions properly. a large number of separate tests must be included in the routine. If these tests are applied manually, a considerable period of time is required for testing each connector and the maintenance costs are therefore unduly high.

Accordingly, the principal object of this invention the provision of a routine test equipment which will automatically routine the connectors in an exchange without attendance, other than that required to start the equipment and to record and repair the faults found.

A further object is to provide a testing equipment which seizes each connector in its consecutive order, applies a series of functional tests to it and. if these tests are proper] y completed, releases the connector to com- Renewed March 28, 1929.

mon usage and seizes the next, to which the same tests are applied.

Another object of this invention is to provide a test equipment which is arranged to camp or not to camp on a busy connector. If a connector is engaged in a call between two subscribers the equipment may be set to either camp on this busy connector and to wait with the application of the tests until the connector is freed again, or the equipment may be set to omit the busy connector and to take the next connector in consecutive order.

A still further object of this invention is to provide a testing equipment arranged to apply a large number of functional tests to each connector, and still further arranged so that it changes from one test to another after the former test has been applied and satisfactorily completed.

A still further object of this invention is to provide a testing equipment, which, when a fault is found will indicate which connector defaulted, and the exact nature of the fault, and which will hold the connector while a signal is operated to summon the attendant to the equipment to inform him of the fault found in the connector.

A further object of this invention is to provide a test equipment which will exercise a (onnector, that is, repeat the same series of functional tests on a connector indefinitely, to make sure that the mechanism functions properly.

The test equipment is set to execute the various tests, by means of keys operated in certain combinations.

Other objects of this invention which are not specifically enumerated above will be apparent from the detailed description and claim which follow:

The drawings comprising Figs. 1 to 5, inclusive, when arranged as shown in Fig. 7, show sufficient details for a clear understanding of the construction and operation of the invention.

Fig. 1 shows part of the test equipment, comprising two distributing switches, the operating magnets of which are designated by the reference numerals 35 and 36, respectirely. This figure shows also in the upper right-hand corner of the drawing conductors anted 1, 2, and 3 which terminate in a connector. in the lower left-hand corner are hown three conductors designated 1, 2. and 3. These conductors are the line and rel rise conductors coming in from a conwhich is being tested. The other \eni shown in this drawing consists of :11 10min keys by means of which the equipment is set to execute the tests; a number of ml signals, and various relays. The 01- on of this equipment will be described sently.

Fig. 2 shows relay equipment; visual signals, and part of an amplifier designated 130.

9, shows various relays and other apparatus belonging to the test equipment which will be described later. However, it may be stated at this point, that the cams designated 210, 212, and 214 belong to a varying machine as is disclosed in the patent to H. F. Obugfell No. 1,523,030 of January 13, 1.925. As is explained in this patent, the obiect of a v rying machine is to operate switches through various resistances and line nges in order to properly margin the ies so that they will operate satisfac- J The varying machine disclosed in this patent is of course modified somewhat to work in connection with the testing equipment disclosed in the present invention. In the lefthuntl upper corner of Fig. 3 is also shown a rota 'y switch 200 having an operating magdo nated 202 and a release magnet desi gnated 201. There is further shown a magnet designated 205 which is adapted to operate an armature 206 and thereby cams 207".- The cam are adapted to operate contacts 208 and 209 in a certain sequence. The purpose and operation of the switch and of the magnit 205 will be described more in detail subsequently.

in Fig. at are shown various relays and sigur s b rnging to the testing equipment.

Fig. 5 shows a connector. This connector is disclosed in the application of R. F. Stehlik, Serial No. 716,577, filed May 29, 1924, whi h nay be consulted for details. It will ssumed presently that this connector is betested by the equipment shown in Figs. 1 to i, inclusive.

Fig. 6 shows a schematic layout of the test equipment, illustrating the relation of this equipment to the connectors in an automatic teiephone exchange.

Fig. 7 is a diagram showing the relation of Figs. 1 to 5.. inclusive.

Before starting the detailed description of the operation, it will be adv ble to make a few explanatory remarks cone ruling the layout and the operation which will a sist in the understanding of the detailed explanation.

It has remarked elsewhere that a series of functional tests is applied to a con nector. These functional tests consist in selecting a connector and of operating this connector under somewhat severer conditions than those encountered in practice. Each function of the connector is checked by the testing equipment and if one of the functions is not executed properly, the connector is held, and a signal is operated to summon the attendant and to inform him of the fault.

It is a well known practice in automatic telephone exchanges to reserve a certain number for test purposes. This num or is usually number 99, and is, of course, reserved for official use. \Vhen this number is selected, the calling party will be connected to a telephone which may be located at the wire chiefs ofitice. A connector may be tested by dialing number 99, and thereby connecting with the telephone of the wire chief. It is obvious that number 99 has been chosen in order to subject the connector to a maximum number of vertical and rotary operations. This test number has been utilized in the present invention. When the number is dialed from an ordinary station, the caller will be connected to the wire chiefs apparatus; however, when the test equipment selects number 99, the wire chiefs substation will be disconnected and the connection will be switched to the test equipment in order to check the functions of the connector. In other words, the test equipment is adapted to automatically call number 99 and to ex tend the connection to its own equipment in order to check and to report the result of the operations of the connector.

When the drawings Fig. l to Fig. 5, inclusive, are arranged as shown in Fig. 7 the complete connection including the connector shown in Fig. 5 can be plainly seen by following the heavy conductors extending through the upper parts of 3, 2. l. and 5. and back from Fig. 5 through the lower part of Fig. 1, and Fig. 2 to Fig. 4.

Depending upon the size of the exchange. there may be a great number of connector If desired, the test equipment will test all connectors in an exchange in their consecutive order. This is done by using primary and secondary distributors and will now be explained briefly with reference to the schematic layout shown in Fig. 0.

Fig. 6 shows a primary distributor desig nated 503 which is connected over an armature 501 of a relay 500 to the test equi i nzeut designated 524. The primary distributor 7103 has access to twenty-five secondary distributors, some of which shown in this drawing and designated 508. 509, and 510. Each of the secondary distributors has access to twenty-five connectors. One of t connectors is designated 517 and shown accessible to the secondarv distributor 509. Utilizing the arrangement shown in Fig.

the primary distributor 503 will have access to six hundred twenty-five connectors. Since the primary distributor 503 is connected to the test equipment 524 over a conductor 528. the test equipment 524 is able to test ix hundred and twenty-five connecton;

It is obvious that the number of connectors accessible to the test equipment can easily be doubled or trebled by adding changeover relays such as the relay 500. It a changeover relay, such as the relay 500 is used, it will be seen that, after the first six hundred and twenty-five connectors are tested through, the relay 500 may be energized to switch the test equipment 524 to another primary distributor such as 503 which again has access to 25 secondary distributors such as 508. Thus, the number of connectors accessible to the test equipment 524-, can be readily increased.

At the right of the connector 517 is shown a relay 519 which is adapted to operate an armature 520. In its normal position, the armature 520 maintains the terminals of number 99 connected with a test station 522. This test station is the one which is usually located in the wire chiefs oflice. Conductor 518 leads to other connectors. Thus, all connectors have access to the wire chiefs test station 522. Relay 519 is provided for one group of connectors.

When the test equipment establishes connection with number 99, the group relay 519 will be operated, to disconnect the test station 522 and to complete the connection back to the test equipment.

The rectangular sections 527, 528 and 529 represent various signal lamps or other visual signals operating in connection with the test equipment 524:.

It will be seen that the section 529 is connected with terminals accessible to the primary distributor 503. This section 529 comprises group signals. \Vhenever a primary distributor such as 503 is operated into connection with a secondary distributor, the corresponding group signal in section 529 will be operated to indicate the group the test equipment has established connection with.

The section 528 includes switch signals and is connected, over conductor 512 with the secondary distributors. When a secondary distributor engages a connector, the corresponding signal in section 528 will be operated.

Section 527 includes fault signals. When the test equipment discovers a fault in a connector, the test will be stopped, and a signal in section 527 will be operated to denote the precise nature of the fault.

It may be mentioned at this point that these signals may be lamps or drops, or any known kind of signal apparatus applicable in the present case. The signals will be referred to as signal lamps.

Briefly the operation is as follows: Depending upon what kind of test is desired, certain keys are operated to start the test equipment. The primary and the secondary distributors are rotary switches, and, having no normal position, are normally in engagement with contacts leading to a connector switch. If it is desired to start the test from a certain connector, there are provisions. as will be seen presently, to operate the distributor switches into connection with this connector.

Assuming that the test equipment has been started, the series of tests will be applied to the connector engaged with, depending upon whether this connector is busy or idle. If the connector is busy, the application of the tests will be deferred. There are, however, provisions to skip a busy connector. lVhen the connector becomes idle within a certain time, the series of functional tests will be applied in rapid succession, whereupon the connector, if found in proper working order, is released to common usage. The secondary distributor then engages the next connector in the group and the tests are applied to this switch.

While the test is in progress, group signals in section 529, and switch signals in section 528 indicate what switch is being tested. When a fault is found, the corresponding fault signal in section 527 will be operated and the test will be stopped until the office attendant notices the trouble and releases the test equipment to normal.

Referring to Fig. 1 there are shown in the lower right-hand corner of the drawing three relays designated 38, 39 and 40. These relays belong to certain groups, each corresponding to a switching relay such as 519 shown in Fig. 6. The energization of these group switch ing relays depends on the operation of the distributor switches. The wipers of the primary distributor switch are designated 47 to 51, inclusive, and the wipers of the secondary distributor switch are designated 52 to 55, inclusive. the motor magnet of the primary distributor and 36 designates the motor magnet of the secondary distributor. The keys and 46 are provided for the purpose of individually stepping the primary and the secondary disice Reference numeral 35 indicates tributor switches to desired bank contacts. 15!;

The group signals are designated 1, 2, and 3, in heavy dotted circles. The switch signals are designated 1 to 12. and 1 to 13, respective.- ly, the numerals being shown in double circles. These latter designations will now be explained a little more in detail.

In the example illustrating the invention. it is assumed that a connector switch frame comprises 25 connectors. These connectors are divided in two groups, the first group including connectors numbered 1 to 12, and the second group including connectors numbered 13 to 25. The relay 38 is the group relay for the first group and the relay 39 is the group relay for the second group. These two group relays are shown fully in operative connection with the test equipment. The group relay 40 which serves a group numbered 8, is shown merely for illustrative purposes and belongs to a further group which may be the last group in the exchange.

If it is assumed that the test is applied to the connector number 1 in group number 1, the group relay 38 will be operated, and the group lamp 1 shown to the left of relay 38 will be lighted. The switch lamp 1 shown above relay 38 in a double dotted circle will also be lighted. The circuit connections will be traced out in detail later on.

In order to explain the functions of the group and of the switch signals a little further, it may be pointed out that wipers 51 and 55 of the distributor switches are shown connected up with the first bank contacts terminating in the group relay 38.

lVhen this relay is energized there are circuits established for the signal lamps 1 and 2 over armatures of relay 38. When switch number 1 has been tested, the secondary distributor will move its wipers 52 to 55, inclusive, into engagement with the connector switch number 2. Wiper 55 of the secondary distributor switch will therefore provide a circuit for the switch lamp number 2. The group relay 38 will be kept energized in a locking circuit extending from its lower winding over one of its own contacts and an armature of the group relay 39.

In order not to complicate the drawings unnecessarily, no switch lamps have been shown between the positions 2 and 11 of the secondary distributor. When the twelfth switch has been tested, which is the last switch in group number 1, the secondary distributor moves its wipers to the terminal designated 13. A circuit is thereby provided for relay 39 which serves group number 2. This relay disconnects the holding circuit for group relay 38, in turn locking itself over a contact of the next group relay in a similar manner as was explained in connection with the group relay 38. The group relay 39 also closes a circuit for the switch lamp 1 shown above the group relay 39.

The test has now proceeded to group number 2, and switch number 1. In this second group there are thirteen switches. No connection has been shown between the position 13 (switch number 1 of group 2) and position 25 (switch number 13 of group 2). When the last connector in group 2, which is connector 13 (position 25 of the secondary distributor) is reached, relay 30 will operate, closing its armature 31, and providing thereby a circuit for the switch lamp 13, indicating that con nector 13 in group number 2 is being tested.

The splitting of twenty-five connectors, lo.- cated in one frame, into two groups, isa common practice and has its reason in traflic re quirements. For a group of one hundred sub scribers there are about ten to twelve connectors necessary to take care of the incoming traffic. In other words in one group of one hundred subscribers ten to twelve subscribers may be called simultaneously. The heavier loaded group receives thirteen connectors and the other group twelve connectors. The number of connectors assumed in the present case, is only necessary in districts having very heavy trafiic. Usually, about ten connectors per one hundred subscribers will be suflicient. If a connector frame is only provided with twenty connectors, that is, two groups each having ten connectors, connectors number 11 and 12 in the first group, and connectors number 23, 24, and 25 in the second group will be missing. Such condition is assumed in the eleventh position of the sec ondary distributor, that is, it is assumed that the eleventh connector in group number 1 is missing. In this case, the private conductor will be connected to ground over a resistance designated 3000. The conductors designated are connected with release conductors of other missing connectors. When ever a secondary distributor encounters such condition, the test will proceed uninterruptedlv.

The purpose of the various keys shown in Fig. 1 will be discussed next. The key designated 41 has the purpose of connecting the test equipment to continually test and retest a certain switch. If it is desired, for example, to subject a certain connector to a continual test, the primary and the secondary distributor switches will be operated into engagement with this connector by means of the manual keys 45 and 46- Then the key 41 will be depressed and the functional tests will be applied to this connector as long as this key remains in operated position. If, during one of the tests a fault is encountered, the equipment will be stopped automatically and the fault will be indicated.

The key 41 in Fig. 1, will be operated whenever a test is started. This key provides ground for the wiper 51 of the primary distributor and for the relay 134 in Fig. 2, respectively, for reasons which will be apparent as the description progresses.

If the key 41 is operated together with key 43, all switches in the exchange will be tested in consecutive order.

Keys 42 and 43, if operated together, serve the purpose of testing all switches in a certain group.

Key 44, when in operated position will effeet the release of the equipment in case it has been stopped either by a, fault found in a connector, or by a busy connector, providing the busy condition. exceeds a certain time interval.

The key designated 70 when in the position shown in the drawing, will cause the test equipment to camp on a. busy connector, and

to summon the attendant after a certain time. If the busy connector becomes free within that time interval, the functional tests will be applied. If it is desired, however, to skip a busy connector, the key 7 0 will be operated.

The reference numerals 16, 17 and 37 designate signal equipment. 16 and 17 may be ordinary signal lam ps or drops, and 37 may be an audible signal. e. g. a buzzer. The signal 16, when operated, indicates that the test has been ended; the signal 17 denotes that a connector is busy. and the audible signal 37 is sounded whenever the attendant is to be summoned to take notice of certain conditions as will be explained presently.

Conductors designated 1, 2, and 3, shown in the right hand upper corner of the drawing are the line and the release conductors terminating in a connector switch. This connector is shown in Fig. 5 and is the one also dis closed in the application of Rudolph F. Stenhlik, Serial No. 716,577, referred to previously. This connector, aside from being accessible to oroinary selectors as shown in the application referred to, is also accessible over the conductor:; 1, 2, and 3, to the secondary distributor switch shown in Fig. 1. The connector is assumed to belong to group number 1 and to be the first switch in this group. When the primary distributor switch and the secondary distributor switch are in the position shown in Fig. 1 they will engage the terminals leading to this connector, thereby extending the conductors 8. 9 and 34, to the test equipment provided relay 20 is in operated position. These conductors have been shown in heavy lilies in order to distinguish them easily from the rest of the equipment.

The terminals of number 99 of the connector shown in Fig. are normally connected over contacts of the group relay 38 to the test station number 99 as was explained in a preceding paragraph. However, when the connector is seized by the test equipment, the group relay 38 will be in operated position extending the connection to the test equipment as shown. This connection has also been indicated with heavy lines designated 1, 2 and 3, leading to the test equipment shown in Fig. 2.

Referring now to Fig. it will be seen that the line conductors 8 and 9 are shown leading over various armatures and over a winding of a relay 109, to the equipment shown in Fig. 3 by way of conductors 218 and The private conductor 34 is wired to a relay 122 and will be traced later.

The line conductors and the private COTE- duetor incoming from a connector which is subjected to a test, which are conductors 1, 2 and 3. are shown branching to Figs. 2 and 4, respectively. These connections will be explained presently.

The remaining equipment shown in Fig. 2- consists of relay 100 to 152, inclusive. the

functions of which will be explained in detail as the description progresses. There are also shown fault signals in this drawing, indicated by heavy circles in order to distinguish them more easily. Each signal designates a certain fault and will be operated if such fault is found in a connector. All of these signals are connected to battery. The battery connections have not been shown by the conventional symbol for the sake of simplicity. It may be mentioned at this point that this is also true of the signals shown in Fig. 1, that is, all the signals shown in Fig. 1 are connected to battery.

The equipment shown in the dotted rectangle and designated 130 is an ordinary ampliiier having a so-called composite relay 131 and a transformer 133. This amplifier is used for various tests which will be apparent from the detailed description.

scrutinizing now Fig. 3 somewhat more in detail, it will be seen that the line conductors 218 and 219 are normally connected together over ari'nature 239 of a relay 238, and that they terminate, over a resistance 216, in cam contacts 213 and 215 of a varying machine. There is also shown a resistance 217 which may be bridged across the line conductors over an armature 234 of relay 232 while the re sistance 216 will be short circuited by an armature 233 of the same relay.

The cams designated 212 and 214 which operate the contacts 213 and 215, and likewise the cam 210 which is adapted to operate the contacts 211, belong to a varying machine, which, it has been mentioned, is shown in Patent No. 1,523,036. Details of the operation of this varying machine may be looked up in this patent. However, for convenience. the purpose of the cams 210, 212 and 214 and of the resistances 216 and 217 will be briefly described.

The varying machine is provided with a motor for operating the cams 210, 212, and 214. \Vhen the test equipment is started, the motor of the Varying machine immediately begins to rotate and operates the cams. The operation of these cams is without function until certain relays have operated to start the application of the functional tests to the connector seized by the test equipment. First of all, this connector must be operated into connection with the test number 99. This is done by transmitting to the connector two digits, each digit consisting of nine impulses. Cam 214 is the impulse cam and is rotated by the motor of the varying machine to close the contact 215 fourteen times per second. The connector, in actual practice, operates only with ten impulses per second. The purpose of the test, it will be remembered, is not to subject the connector merely to conditions which are encountered in practice but to subject the connector to abnormal tests which the connector must undergo without defaulting.

Therefore, instead of operating the connector with ten impulses per second, the varying machine will deliver fourteen impulses per second by means of the cam springs 215. The impulse cam 214 will be rotated by the varying machine continually. Therefore, a discriminating means is necessary to determine the number of impulses to be transmited to the connector. This means is the impulse short circuiting cam 212, which closes the contact 213 whenever the proper number of impulses have been transmitted by the cam contact 215. The cam 210 which operates its contact 211 is provided for the purpose of determining when the impulses are to be effective to operate the connector.

Referring to the resistances 216 and 217, it will be seen that resistance 216 is normally in series with the line conductors 218 and 219. \Vith the relay 232 energized, however, the series resistance 2 16 will he short-circuited, and resistance 217 will be bridged across the line. The connector will fi rst be operated with the relay 232 deenergized and the resistance 21-6 in series with the line circuit. This resistance represents the maximum resistance under which the line relay of the connector must operate without defaulting. However, the line relay of the connector must also respond properly in'case there is a certain permissible leakage on the line. This leakage is represented by the resistance 217 which will be connected across the line by relay 232.

The rest of the equipment shown in Fig. 3 will be readily understood from the detailed description.

Fig. 4, when arranged below 2 shows the line conductors 1 and 2 coming in from the connector subjected to a test, terminating in the test equipment. These line conductors have been shown in heavy lines and all circuits pertaining to the line conductors ,have likewise been shown in heavy lines in order to simplify the tracing of circuits. The reference numerals 5, 6, 7, and 9 are signal lamps similar to the signal lamps shown in Fig. 2. 333 indicates a tone machine which is provided for a certain functional test. The interaction of the various relays shown in this Fig. 4 will be made clear subsequently.

The equipment is shown at rest, all relays and other apparatus being in normal position. Throughout the drawings are shown :a plurality of ground and battery connections but it will be understood that this has been done merely for convenience of description and that there is "only one battery, with one pole grounded, provided in the exchange.

With the above preliminary remarks in mind the detailed description will now be proceeded with. The drawings should be arranged in the order as shown in Fig. 7.

The primary distributor has its wipers 47 to 51, inclusive, connected to the wipers 52 to 55, inclusive, of the secondary distributor.

The latter has engaged the first set of contacts, and the Wipers 52, 53, and 54 are therefore in engagement with the line conductors 1 and 2 and with the release trunk 3, leading to the connector shown in Fig. 5.

Referring to this connector, it will be seen that the line conductor 1 terminates in the upper winding of the line relay 405, and battery, while the lower line conductor 2 terminates in the lower winding of the line relay 405 and ground. When this conductor is idle, all parts shown in Fig. 5 are in the position shown. When this connector is busy, however, the relay 410 will be energizcd keeping ground connected to the release trunk 3 by way of its armature 411.

It will be assumed, that the connector shown in 5 is desired to be subjected to a continual test. This requires the operation of the keys designated 41 and 41. It will be further assumed, that the test equipment is set to camp on a busy connector, that is, the key is in normal position.

It shall further be assumed that the connector is engaged. Relay 410 is therefore in operated position and ground is connected to the release trunk 3. A circuit will be closed for the operation of relay 15 shown in 1 as follows: battery, relay 15, closed contact of key 70, armature 22, wiper 49 of the primary distributor, wiper 54 of the secondary distributor, conductor 3, Fig. 5. conductor 3, armature 411 to ground. Relay 15 operates. At its armature 17, relay 15 disconnects relay 20, and at its armature 18 this relay switches the ground provided by key 41 from conductor 33 to conductor 29. The key 41 being in operated position ground is connected now to the conductors 14 and 29 as follows: ground, key 41, armature 28 and its resting contact, closed contact of key 44, armature 18 and its make contact, conductor 29. Conductor 14 is also grounded in a circuit branching off from armature 18.

Tracing the conductors 29 and 14 to Fig. 3 it will be seen that relay 226 is connected to the conductor 29, while the conductor 14 terminates in a. normally open contact of re lay 257. A circuit is therefore closed for the operation of relay 226. Upon operating, relay 226 closes a circuit at its armature 227 for the operation of relay 220. This latter relay energizes and connects at its armatures 222 and 223 a circuit for the operation of relay 224, which may be traced from battery, winding of relay 224, make contact and armaturc 222, normally closed contact controlled by armature 261, closed contact and armature 259. armature 223 and its make contact, and to the grounded conductor 29.

The magnet 205 shown at the left side of drawing Fig. 3 is connected in the above circuit parallel to the relay 224. The magnet 205 operates its armature 206, thereby moving the cams 207 towards the contacts 208 and 209. There are two such cams 207, only one having been shown for convenience of description. One of these cams is adapted to operate the contact 208 and the other cam is adapted to operate the contact 209. Immediately upon the operation of the magnet 205 and corresponding displacement of the cams 207, the cams are both under the influence of a pawl operated by the Varying machine, and will be rotated in a counterclockwise direction. The pawl mechanism has not been shown in order to keep the drawing as simple as possible. It is mounted on the varying machine and the pawl is constantly operated by team arrangement, as long as the machin in operation.

The cam adapted to actuate the contact 209 will need a certain time to rotate into its operating position. It will of course be under- StO'O'd that the time for operating this Contact depends on the size and shape of the cam and on the speed of the pawl mechanism, and that this time can be lengthened or shortened according to the requirements. For the purpose of description it is sufiicient to know that the contact 209 will be closed a certain time after the energization of the magnet 205.

The closure of cam contact 209 causes an impulse to be transmitted to the rotary magnet 202 of the switch 200. At the same time, certain relay actions will cause the disconnection of the magnet 205 and consequently, the opening of contact 209. The magnet 205 is then energiz ed again and causes the delayed rotation of cam toward contact 209. When contact 209 clo'ses for the second time, the above operations are repeated. Thus, the switch 200 is operatedand advances its wipers 20a and 20 2 over the bank contacts. After a while, the wiper 203 will reach a contact to which is connected the conductor 257. When this occurs, the relay 257 will operate and close an alarm circuit to advise the atte'nda'nt that the connector is busy.

The connector busy lamp 17 in Fig. 1 was lighted immediately over conductor 19' to ground at armatufre 221 of relay 220.

It was assumed that the connector was to be subjected to a time test, i. e., that it was to be tested and re'tested continnally. In such a case the attendant has most likely a (lefi nit purpose in r'nind, and he will watch the equipment. ,The busy lamp will inform himv of conditions encountered by the test equipment. n audible signal therefore unnecessary, A However, if a' busy connector is encountered during the time the equipment is set to test the connectors in consecutive order, the busy lamp. 17 will be lighted, and, in addition, an audible signal will be operated after a certaintime', to summon the attendant.

If the'cennectorbecomes idle within the allowed time interval, the functional tests will be applied and the signal operating equipment will be disconnected.

The operations intimated above will now be explained in detail.

When contact 209 is operated, a circuit will be closed for the operation of relay 260 from battery, winding of relay 260, closed armature 225 of relay 224, cam contact 209, to ground connected by closed armature 221 of relay 220. Relay 260 operates its armature 261 thereby disconnecting the magnet 205 and the rela 224 from the circuit. However, a circuit or the rotary magnet 202 is closed in parallel to the circuit of relay 260, which extends from battery, winding 202 of the rotary magnet, cam contact 209, contact and armature 221 of relay 220 to ground. The rotary magnet operates and steps the wipers 203 and 204 onto the first bank contacts. It will be seen, that the relay 257 may be con nected to a contact accessible to the wiper 203 of the switch 200. The wiper 203, in advancing, will therefore complete a circuit over the conductor 257 for relay 257. The time in which the relay 257 is operated depends on the connection of conductor to one of the contacts of the bank accessible to wiper 203.

Returning to the operation of relay 200 and of the rotary magnet 202, it will be remenr bered that the circuit for the relay 22% and the circuit for the magnet 205 were opened. Accordingly, magnet 205 releases its armature 206, thereby returning the cam contact 209 to normal position as shown in the drawing. Upon the release of relay 224, the circuit for relay 260 is opened at the armature 225 and relay 260 releases, closing the contacts controlled by armature 261. The rotary magnet- 202 thereby disconnected and a circuit is again closed for the operation oi the mag net 205 and the relay 224 over the original energizing path. After a certain time the cam contact 209 will close again connecting the rotary magnet to advance the switch wi pers a further step, and closing a circuit for relay 260. The relay 260 again disconnects the magnet 205 and opens the circuit of relay 22-1, and the latter releases the circuit for the rotary magnet and for the relay 260. Thus by the interaction of the relays 224 and 260 on the one hand and of the magnet 205 operating the cam Contact 209 on the other hand, the rotary switch 200 is operated to advance its wipers over the bank contacts.

\Vhen wiper 202i reaches the contact to which the conductor 25? is connected. relay will be energized in an obvious circuit. This relay closes its armature 25S connecting the conductor 14, which, it will be remcmiii bered, grounded from the key 41, with lay 220. At the present time. this connection is of no consequence. other than to connect a parallel ground to hold the relay 220 ener gized. At its armature 259 the relay 257 disconnects the magnet 205 and the relay 224. At the make contact of armature 259 a circuit is closed for an alarm signal provided to indicate to the attendant that the switch is busy. The circuit for the alarm signal is, as has been mentioned, effective only during the consecutive test, and is closed as follows: ground on conductor 29 (th s conductor is grounded from the key 41, Fig. 1) closed contact and armature 223, armature and its make contact, conductor 12, and to the alarm signal 37 in Fig. 1. Since relay is held energized, ground is connected to conductor 19 leading to Fig. 1 and terminating there is the busy lamp 17. This lamp is therefore lighted and denotes that the switch is busy.

Nothing will happen as long as the key 41 is depressed. Relay 257 will stay operated to ground over wiper 203 of the switch 200 preventing further operation of the magnet 205 and of the relay 224, while the relays and 220 are operated from ground on conductors 14 and 29. Should the attendant release the key 41, ground will be disconnected from these conductors and relays 220 and 220 will deenergize. The release of relay 226 opens the locking circuit of relay 220, and the release of relay 220 opens the circuit for the connector busy lamp 17 by removing ground from the conductor 19. At the same time, a circuit is closed for the operation of the release magnet of switch 200 from ground, armature 221 of relay 220, wiper 201-, releas magnet 201, to battery.

If it is assumed that a busy switch is encountered while the test equipment is connected to test the connector switches in consecutive order, the key 41 and the key 43 will be depressed. Vhen a busy connector is encountereo under these conditions, the pro cedure of the operation will be precisely the same, and when relay 257 energizes, the alarm signal 37 will be operated. In a consecutive test the equipment is not under constant supervision of the attendant but operates en tirely automatically, testing one connector alter the other. Under these conditions an alarm signal advising the attendant that a connector is busy and that the test equipment camps on this busy connector is of course necessary. If the attendant desires he may release the test equipment by simply operating the key 44, or he may investigate whether the connector which was signalled busy, is faulty, or actually engaged in conversation.

\Vc shall return now to the operation of the switch 200 while the test equipment camps on the busy connector. However, it will be assumed that the switch 200 has not been advanced far enough to operate the relay 25".", when the connector becomes idle.

Referring to Fig. 5, when this connector is released the relay 410 will return to normal and will remove ground from the release conductor 3. Accordingly, relay shown in ig. 1 releases. The key 41 being depressed ground will now be connected over armature 18 of relay 15 to conductor 33. Following this conductor to Fig. 2, it will be seen that it connects with conductor 13 over an armature 129 and its resting contact. Conductor 13 has been shown heavy in order to easily distinguish the same from the rest of the circuit. This conductor 13 may be termed a common holding conductor. It provides ground for a great many circuits, as long as relays 15 and 126 are in resting position and one of the keys 41 or 42 is depressed.

Relay shown in Fig. 1 will now operate from battery, winding of relay 20, resting contact and armature 17 resting contact and armature 11, to ground on holding conductor 13. Upon operating, relay 20 closes its armatures 24 and 25 switching the line conductors 8 and 9 through to the line conductors 1 and 2 terminating in the connector, Fig. 5. At its armature 22, the relay 20 disconnects the release trunk 3 of the connector from the winding of relay 15 and connects the release trunk to the conductor 34 terminating in Fig. 2 in a normally open contact 121 of relay 116 and in the winding of a relay 122. At its armature 23, the relay 20 connects itself in a locking circuit to the holding conductor 13.

Upon the release of relay 15, ground was disconnected from the conductor 29, thereby deenergizing the relay 226 in Fig. 3. The release of this relay is followed by the release of relay 220, and, when the latter relay deenergizes, it opens the circuit for relay 224 at its armature 222. The relays 226, 220, and 224 therefore deenergize in succession. Remembering that the holding conductor 13 is connected to ground at this time, it will be seen that a circuit is closed for the energization of magnet 205 from ground, holding conductor 13, normally closed contact controlled by armature 255 of relay 253, closed contact and armature 223, armature 259 and its resting contact, normally closed contact controlled by armature 261, conductor 13", winding of magnet 205, to battery. The operation of coil 205 has at the present time only the result of moving the cams 207 into operative relation with the cam contacts 208 and 209. The cams 207 will be rotated in a counter clockwise direction and will at the expiration of a certain time interval operate one of the contacts as will be described presently. For the present time, it is suflicient to remember that the coil 205 remains operated while the test equipment is in operation. During the time the test equipment was camping on the busy connector, the rotary time switch 200 was advanced to a certain position. When the connector switch became idle, relay 15 deenergized removing ground from the conductor 29 and causing the release of 200, in order to return the switch to normal:

position;

Relay. 20'energizeel upon'the release of the relay L5 when the connector became idle. At its anmatune 21, relay20 closes an obvious circuit for relay 5, and the latter relay, upon operating: closes circuit for relay- 10. Relay 5prepares at its armature 7 a circuit for the motor'magnet 36 of the secondary distributor. This circuit is, at the present time ineffective. Its utility will'be discussed later. Relay 10 at its armature 11, opens the original energizing. circuit. of relay The line conductors 1 and2 of the connector Fig. 5, are now connected to the test equipment as follows: upper winding: of the line relay 405, normally closed contact controlled by armature 402, line conductor 1, to Fig. 1, Wiper 52 of the secondary distributor, wiper of the primary distributor, armature and its make contact, conductor 8 to Fig. 2, upper winding of relay 109, normally closed contact controlled by armature 101, conductor 218 to Fig. 3, break contact and armature 239 of relay 238, conductor 219 to Fig. 2, normally closed contact controlled by arma ture 102, armature107- and its resting con tact, conductor 9 to Fig. 1, make contact and armature 24, wiper 48 of the primary distributor, wiper 53 of the secondary distributor, conductor 2 to Fig. 5, normally closed contact controlled by armature 403, lower winding of the line relay 405 to ground. There is therefore a loop circuit provided which includes both windings of the line relay 405'of the connector and the upper Winding of: the relay 109- of the test equipment.

The first test to be appliedito the connector is for open loop. This means in the phraseol'ogy of the art an interruption of the loop circuit over which the line nelay normally operates. If the loo) circuit is present the line relay 405 will operate in series with the upper winding of relay 109. The latter relay, of course, energized also.

If the loop'circuit is open, neither the relay 405 nor the relay 109 will operate. At armaturellO, the relay 109, will keep a circuit prepared for the signallamp 1 over con ductor 262 to Fig. 3 and from there over the restingcontact and armature 231 to armature of relay 253.

The lest equipment is set to apply the series of functional tests to the connector. It isobvious that these tests can not be executed satisfactorily on account of relay 405 of the connector not being operated. The magnet shown in Fig. 3, as will he remembered, is connected to ground on the holding conductor. After a certain time. the cam. contact 208' will be operated, providing a circuit for the relay 253 from battery, winding 253, conductor 253, camcontact 208, resting; contact and armature 221 to ground. Upon'operating, the relay 253 closes its armature locking itself to the holding conductor l3, and completing at armature 254 circuit over conductor to Fig. 2T0 light the fault lamp No. 1. Alt armature 256 a circuit is provided. extending over' conductor 121m Fig; 1 temperate an alarm:

ik-gaiinas'in the former'case, the!alarm is only of utility in case ofas continuous test. Since it was-assumed,.lu'iwever,.thatonly one switch is tobetestcd repeatedly. it will read ily be seen that anaudihle'signal is unnecessary because the attendant will be present and will be adv-isedzof thefault by the lighting of lam yNo. 1.

iifi the loopcircuit ispnesent, the line'relay 405 of the connector, anditherelay 109 whichin series with the line relay, will energize. Relay 109 locks itself to the holding conducton 13-over its armature 112. At armature L111 the upper winding of relay 109' is short cincuited to provide a dialing circuit for the connector which includes only the series test resistance 216 in Fig. 3.

At. its armature 110 the relay 1'09 disconnects the fault lamp No. 1 and extends the signalling. circuit to fault lamp 2 by Way of armature 1230f relay 122.

Referring now to'the connector Fig. 5, it will be remembered that the line relay 405 was operated oven the loop circuit. It closed its armature 406. Relay 410 which. is connected to ground, and short circuited over the normally closed contact controlled by armature 406, operatesnow in series with the relay 4'15 and the vertical magnet 445. The circuit may be traced from'ground, winding 410, make contact and armature 406, closed oif normal contact 460, relay 415, winding of the vertical magnet 445 to battery. The relay 415 and the vertical magnet 445 do not operate inlthis circuit on account of the high resistance of the release relay 410; Upon cperating,.relay 4l0,.at its armature 413, disconnects the release magnet 462, and prepares certain operating circuits at the make contact of this armature. At its armature 411 the relay 410'connccts ground to the release trunk?) in order to busy the switch The test equipment will now test for the satisfactory connection of busy ground to the release trunk. It will be seen that the release trunk conductor 3' of the connector extends back't'hrough Fig. 1 to conductor 34, terminating in Fig. 2in the relay 122. Relay 122 will operate if the connector'ha's connected guarding ground to the release trunk 3. Relay 122'switches its armature 123. disconnecting thereby the fault lamp No. 2' and extending the signal circuit tothe fault lamp )lo. 3 o er an armature 103 of relay 100.

1t is obvious that the relay 122 cannot operate if no ground is present on the release trunk leading to the connector. The coil 205 of the test equipment being energized, the cam contact 208 will be closed after an interval to energize the relay 253, and a circuit will be completed for lighting the signal lamp N o. 2.

Assuming that the connector, so far, is in proper working condition, relay 122 will operate as explained and switch the signalling circuit to lamp 3. Relay 122 closes also its armature 125 thereby completing a circuit for the relay 113 from ground, armature 125 and its make contact, winding 113, conductor 113 to Fig. 4, armature 326 and its resting contact, to battery. Relay 113 operates and closes its armature 114 thereby connecting ground to the conductor 211 which may be traced to the cam contact 211 in Fig. 3. This contact is operated by the trip cam 210. It has been remarked previously that the purpose of the trip cam is to determine when impulses generated by the varying machine are to be ell'ective. This is the case now, the connector being ready to receive the impulses. The trip cam 210 Will close the contact 211 and thereby complete a circuit for the operation of relay 241 as follows: battery, winding 241, break contact and armature 240, armature 248 and its break contact, conductor 241, cam contact 211, conductor 211, to Fig. 2, conductor 211, armature 127 and its break contact, armature 114 and its make contact, to ground. The relay 241 operates therefore, closing its armature 242 and preparing thereby a circuit for the relay 238 in series with its own winding and over armatures 247 and 252 to the grounded holding conductor 13. The circuit for relay 238 will be etlcctive when the trip cam opens contact 211, allowing relay 238 to energize. Prior to this point, the relay is shortcircuited.

Upon the operation of relay 238, the loop circuit is opened at armature 239 and is extended over the series resistance 216 to the cam contact 215. This contact is controlled by the impulse cam 214 which, as has been e:\' plained, revolves constantly, closing the contact 215 fourteen times per second. The loop circuit to the connector will therefore be interrupted in rapid succession and will operate the line relay accordingly. Two series of impulses will be transmitted in this manner, over the loop circuit which includes the series resistance 216. Each series of impulses consists of nine short interruptions in order to operate the connector into engagement with terminals of number 99. The impulse short circuiting cam designated 212, which is operated by the varying machine, closes its contact 213 upon the termination of the first series of impulses and opens this Contact again in order to permit the second series of impulses to be transmitted.

Referring to Fig. 5, the connector will be operated 9 steps vertically and 9 steps rotary, and advance its wipers 451, 453 and 455 onto the terminals 452, 454, and 456. These terminals correspond to number 99. A detailed account of the vertical and rotary operations of the connector is deemed unnecessary since reference was made to an application in which this connector is disclosed and described in detail.

It will be seen that the terminals 452, 454, and 456 are wired to Fig. 1, terminating there over conductors 1, 2 and 3 in armatures of relay 38. From there these conductors extend normally to a telephone set which may be located in the wire chiets oflice. When the connector, Fig. 5, was seized by the test equipment, or rather to say, when the start key 41 was operated, a circuit was closed for tile operation of the group relay 38. This circuit is an obvious one and includes the wipers 51 and 55, of the primary and of the secondary distributors. Upon operating, the group relay 38 closes an armature to connect its lower winding in a locking circuit extending to ground on key 41, and including normally closed armatures of other group relays.

The group lamp No. 1 which is shown to the left of the group relay 38 is thereby connected in a circuit parallel to the holding winding of the group relay and will light to indicate that a test is being executed in group No. 1. The uppermost armature of relay 38 closes to light the switch lamp No. 1 in order to indicate what switch is being tested in this group.

The group relay 38 being in operated position, it will be seen that the line conductors 1, 2 and 3 are disconnected from the telephone set number 99 but instead connected to the test equipment. The private conduc tor 3 terminates in relay 100, shown in Fig. 2, by way of a normally closed contact 230 of relay 228 shown in Fig. 3. The line conductors 1 and 2' terminate in the test equipment as follows: conductor 1, normally closed contact controlled by armature in Fig. 4, closed contact and armature 308, winding of ring test relay 329, condenser, 329, normally closed contact controlled by armature 322, armature 328 and its break contact, and back to the connector over the conductor 2. The ring test relay 329 in series with the condenser is therefore bridged across the line conductors 1 and 2.

Returning now to the operation of the connector, when the wipers of this switch engage the terminals 452, 454, and 456, the switching relay 435 energizes, closing its armature 438. This armature connects ground to the private conductor 3'. Under ordinary conditions, when the connector is used for connecting with a subscribers line, this ground circuit serves for holding the line relay energized.

The next test applied to the connector is for the purpose of checking whether the connector was properly operated into eng geinent with the terminals of number 99, and whether ground was connected to the private conductor. This is done in the following manner: A circuit will be closed for the operation of the relay 100 shown in Fig. 2, if the private con ductor 3 was properly grounded. Relay 100 energizes and disconnects at its armature 103 the circuit for the fault signal lamp No. 3, at the same time extending this circuit to fault signal lamp No. 4.

In case the connector did not properly respond to the digits transmitted by the testequipment, or in case ground was not connected to the terminal 454 of the private conductor 3, there will be no circuit for the energization of relay 100. Accordingly, the lamp 3 will remain connected to the prepared signalling circuit. Upon closure of the cam contact 208, and consequent operation of relay 253, the signal lamp 3 will light to inform the attendant that the connector had defaulted on this particular test. However. it the connector has responded properly, relay 100 cuergizes as described. At its arinatures 101 and 102 the relay 100 disconnects the line conductors from the impulse equipn'icnt shown in Fig. 3, and extends them to other test equipment. The line circuit includes now the lower winding of relay 147.

It will be seen that the relay 147 has two windings. One of these windings is connected to battery and to the grounded hold ing conductor 13. The relay 147 is an elcctropolarized relay and does not operate its armatures When its upper winding alone is connected to a circuit. However, when the lower winding of relay 147 is also connected to a circuit, providing the current flowing in this circuit is in the proper direction, the relay 147 will energize. The lower winding of relay 147 is, as has been explained, included in the line circuit of the connector, and. it all connections are in correct working order, the current flow through the lower winding of relay 147 will be in the right direction and will cause the energization of this relay in series with the winding of line relay 405 of the connector. This constitutes a test to ascertain whether the line conductors are wired correctly or whether they are reversed. If the line conductors are reversed, the current flow in the lower winding of relay 147 is in a direction to keep the armatures of this relay at normal. If the line conductors are properly connected this relay operates and close a circuit for the operation of relay 141. The lat ter relay disconnects the fault signal lamp No. 4, and extends the signaling circuit to fault lamp 5.

At its armatures 143 and 146 the relay 141 prepares a circuit for the amplifier shown 130. This circuit will be effective at a later stage of the test and shall be explained presently. At its armature 144, the relay 141 extends ground from the make contact of armature 149 to the conductor 211, which branches at the left to the test equipment shown in Fig. 3, and the right to the equipment shown in Fig. 4. Following this conduct-or 211' to Fig. 4, it will be seen that a circuit is closed for the operaton ot the relay 300. The latter relay operates and at its armature 301 disconnects the relay 320, at the same time linking the conductor 2.11 to the conductor 147'. At its armature 302 the relay 300 opens a point in a circuit which shall be described later.

The next step in the sequence of operations of the connector consists in applying ringing current to a called line. The test equipment will therefore test now whether the connector applies ringing current properly.

It will be remembered that the line conductors 1 and 2 are at the present time connected to a circuit which includes the ring test relay 329 shown in Fig- 4. When the connector applies ringing current, this relay will ontraie as follows: Fig. 5, ringing current source 464. armature oi the ringing intcrruptcr relay 405. normal contact and armature 424 of the "lg-cutoff relay 420, armature 442 and make contact, wiper 455, terminal 456, line conductor 2, normal contact and armature 328 of relay 324. normally closed contact controlled by armature of relay 320, condenser 320, ring test relay 329, armature 30S and its break contact, normally closed contact controlled by arn'iaturc line conductor 1, hack to the connector, terminal 452, wiper 451, make contact and armature 436, armature 421 and its resting contact, lower winding of the ring-cut-oil relay 420, to ground. The ringing relay 329 in the test equipment energizes over this circuit in response to the first ring sent out by the connector. lt closes its armature 330 and thereby completes a circuit for the relay 314, from battery, winding 314. resting contact and arn'iature 311. make contact and armature 330, conductor 141, make contact and armature 149 of relay 147. to ground. Relay 314 energizes in this circuit. At its armature 315 relay 314 opens the prepared circuit for the signal lamp No. 5 and extends the signalling circuit over arinatures 306 and 321 to the signal lamp No. 6. Relay 300, it will be remembered, is in operated position at this time. At its armature 316. the relay 314 prepares a circuit tor relay 309 in series with its own winding, to ground on conductor 211. However, relay 309 can not operate at the present moment on account of being short circuited.

If the connector does not apply ringing current. relay 329 will not operate and the relay 314 will therefore remain normal. After the expiration of a certain time a circuit will be closed for the fault signal lamp No. 5 inclieating to the attendant that the connector failed to apply ringing current.

The ring test relay 3:29 diiienergizes at the end of the 'inging period, reniovin the -1 circuit from relay 309 and allowh t lay to operate. At its armature 310 rel "3' 309 opens the link circuit extend ,5 to cenductor 147, interrupting thereby the circuit of relay 300, and connecting;- ground iii-o conductor 211 to the upper winding 01 t polarized relay 317. The latter relay does not operate in response to the energ its upper winding alone, but can g'ize if its lower winding: is connected to a rent in the proper direction. At its armature 311, relay 309 disconnects the orig nal energizing circuit for relay 311 but the lay holds itself in a locking circuit with relay 300 to the grounded cond' 211. At its armatures 312 and 313. f 309 connects the resistance; 331 T3. L: certain relation to the inc':11...;; ductors 1 and 2.

The circuit for relay 300 However, this relay is slow-r T its armatures in operated 1 tain time. irri'natiire 302 f 1 fore keeps the circuit extcnd turc 312 to the middle point oi it; 331 and 332 open. Relay 300. hei ated position. keeps the arinatr 313 closed. The two resnt are therefore connected in se ie across the line conductors 1 and 1:; lel to the ringing relay The test equipment executes a 10;. for premature ring cut-oti. Th' fault caused by poor adji 's nier cut-oft relay in the c nn. ctor conditions, which permit the 'i lay 420 of the connector. to one? turely before the subscriber has ac plied.

The ring cut-off relay 120, of the co is now connected in se ies with the two resistances 331 and If the ri: 5 relay is properly aciusted. it cannz ate over these resistances. However adjustment is faulty, or. it other cc exist in the connector to cause a. prenr: ring-cut-otl, the relay 120 wi l e erg this happens, the cut-ott relav connects the ringing generator. cennecti e the back-bridge relay 400 w th d ground to the line conductor 1 operating, the back-bridge relay it the line conductors 1 and 2 tertuiiiatii battery and ground in the line relay spectively. Relay 147 which. as ha b en stated, is a polarized relay. has; wer winding connected in the circuit of the li e relay of the connector. and was ere. .ed in this circuit. hen the baek-brid re ax operates now, it reverses the line cmuluetw-s and thereby the current flow in the 10 ir- Iault lamp 6. The tault lamp 6 will he uted alter a while to in form the attendant it the connector has prematurely disconted ringing current. Assuming, however, that the connector has functioned properly, relay 300 will deenere and disconiect lamp 6 at its armature fit armature 301, a circuit is prepared relay 320, and at armature 302, the reau 331 is short circuited, leaving re- ':;i;ce 332 alone in series with the ring- 1 -05! relay 420. The latter relay should operate and cut-oil the gen rator. The ti ns which take place in this case will ed subsequently. It shall first be I; the ring); cuboii relay 120 tails in s ries with resistance 332. center or transmits another ringing a- .ne equipment. The ring test rnerg izaes again, and closes its ar- 330. Since conductor 141 is conl to ground at the make contact and ure 140 of relay 147, and since relay r rated in series with relay 314, it obvious that a circuit is completed =11 the rnergrixation ot the ring-test relay for the operation of relay 303, by way (it arn'iatures 311 and 330. Relay 303 prewar. at its armature 304, a circuit for re- 305. This latter relay, it Will be seen, is connected to the grounded conductor 211'.

loi as the ring-test relay 329 is operated relay 305 cannot energize on account short circuited to ground over arma- 311, 330, conductor 141. to ground make contact and armature 149 of relay pen the termination of the ringing impulse, relay 320 deenergizes and remove the short-circuit from relay 305. This relay opmite now. At its armature 308, relay 305 opens the ringing circuit; at armature 307, the relay 320 is disconnected; and at armature 306 the fault lamp 7 is connected to me ig'nalling circuit. Thus, the further applic 'on of ringing current is prevented, the tes e4; uipnient is locked in the achieved stage, and the rault lamp 7 will be lighted to advise th attendant that the connector failed to diset ringing current.

issuming, however, that the connector functions properly, the ring cut-01f relay 420 will energize in series with the resistance 332. This happens upon the release of relay 300, which short-circuits the resistance 331, and before a second ringing impulse is transmitted to the test equipment. The relays 300, 303 and 305 are, therefore, at rest, while the rel 300 and 314 are energized. The relay 147 is, at this moment, also energized, its circuit over the lower winding including the windings of the line relay 405 of the connector. it will be seen that the fault lamp 8 is now, connected to the signalling circuit, over armature 151 of relay 147, conductor and the armatures 32 306 and 315.

When the ring cut-off relay 420 energizes at this instant, it connects the back-bridge relay 00 across the called line, and this relay energizes now and reverses the current flow over conductors 1 and 2. If the current rere sat takes place in the proper manner, the relay 147 will deenergize and switch the signalling circuit from fault lamp 8 to fault lamp 0. However, if the current reversal is not executed properly, relay 147 remains operated, and the fault lamp 8 will be lighted ...-al the trouble.

It no fault exists as far as the reversal of current is concerned, relay 147 will deenergize, and switch the signalling circuit to fault lamp as explained. Relay 141 remains operated over a circuit including its armature 144, to ground on conductor 211. Relay 147, upon deenergizing, connects ground to conductor 147 at its armature 149 by way of make contact and armature 145 of relay 141. :tclay 320, in Fig. 4, energizes now over an obvious circuit including the armatures 307 and 301, and conductor 147. At its armaturts 322 and the relay 320 disconnects the ring test equipment, at the same time connecting the lower winding of relay 317 across the line conductors 1 and 2. The relay 317 is, as has been stated, an electro-Polarized rub", and its upper winding is connected to :1 circuit extending over an armature 310 of relay 309 to ground on conductor 211'. This relay is adjusted to operate when its lower m ling is connected to a circuit in series with the winding of the back bridge relay 400 of the connector, 5. However, the operation of relay 317 is only possible if the current flow in the circuit is in the proper direction.

The test equipment checks now whether or not the wipers 451 and 455 are connected up pro erly, that is to say, whether these wipers are reversed. If these wipers are reversed, the current flow in the lower winding of relav 317 will prevent an operation of this relay. It will readily be seen that the armature 318 controlling the circuit of the fault slg" il lamp No. 9 will then remain in resting position and the signal lamp 9 will be lighted in the usual manner to advise the attendant of the fault.

If it is assumed, however, that the Wipers in the connector are connected up properl with respect to the windings of the hac bridge relay 400, the current fiow inthe lower winding of relay 317 will cause the operation of this relay. At its armature 318, relay 317 disconnects the prepared circuit for the fault signal lamp No. 9, at the same time switching the signalling circuit over conductor 266 and over an armature 140 of the relay 136, to the fault signal lamp No. 10. At its armature the relay 317 completes a circuit for a. tone machine 333, over a transformer wind.- ing 33 At its armatures 317 and 317", the relay 317 connects the secondary Winding of the transformer to the incoming line conductors 1 and 2.

The next test applied by the equipment is for the existence of the circuit provided for the transmission of voice currents. The tone machine 333 shown in Fig. 4 and the transformer with its windings 334 and 335 are provided for this purpose.

A tone is now transmitted by means of the secondary winding 335 of the tone transformer and over the line conductors 1 and 2 to the talking conductors of the connector and through the condensers back to the test equipment over conductors 1 and 2. Following these conductors to Fig. 2 it will be. seen that they terminate there in conductors designated 8 and 9. Conductor 8 may be traced now over the short circuit of the upper Winding of relay 109, make contact and armature 101 of relay 100, armature 150 and its resting contact, armature 146 and its make contact, secondary winding of the transformer 133. armature 143 and its make contact, resting contact and armature 148, armature 102 and its make contact, armature 107 and its resting contact, and thence over conductor 9, through Fig. 1, and from there as conductor 2 to the connector. The current induced thus into the secondary winding of the transformer 133 is now amplified through two stages of the amplifier designated 130 until the composite relay 131 is reached. If the current induced by the tone machine 333 is transmitted correctly through the connector, in other words, if the circuit provided for the transmission of voice currents is in proper working order, the composite relay 131 will operate and open its armature 132. Relay 134 which is in energized position as long-as the composite relay 131 is at rest, deenergizes now, closing its armature 135 and completing thereby a circuit for the relay 136. The latter relay in operating, disconnects at armature 140 the prepared circuit for the fault signal lamp No. 10, at the same time extending this signalling circuit over armature 118 of relay 116 to the fault signal lamp 11. At armature 138 the relay 136 connects itself n a locking circuit to ground at armature 114 of relay 113. If a fault exists in the voice current transmission circuit, relay 131 will not operate. Accordingly, relay 134 remains in operated position and relay 136 cannot energize. The circuit for the fault signal No. 10 will remain closed and this signal will be lighted in the usual manner. It may be mentioned at this point. that the resting contact of armature 132 of the composite relay 131 is normally disconnected from ground at key 41 shown in Fig. 1. When the test is started, this key is operated and provides ground for the operation of relay 134 over armature 132 of the composite relay.

It will be assumed that the voice current transmission circuit is in proper working condition. Accordingly, the relay 136 will energize and lock itself over its armature 138: at armature 140 the fault signal circuit is extended to the fault signal No. 11, and at armature 137 a circuit is closed for the operation of relay 106. At armature 139, the relay 136 opens a point in the signalling circuit for lamp 14. This, however, is of no consequence at the present stage of the operation.

Referring to the connector, Fig. 5, this switch is of the type which releases when the last party replaces the receiver. The operation is explained in detail in the application referred to. However, for the sake of convenience, the functions of the connector will be explained at this place as far as they pertain to the operations in connection with the test equipment.

It shall be assumed that the called subscriber does not replace his receiver immediately upon the termination of the conversation, but leaves his receiver off the hook for a time, while the calling party has restored the receiver.

The following conditions exist in the connector while the subscribers are talking: The busy relay 425 is disconnected over an armature 439 of the switching relay 435. The switching relay 435, and the ring-cut-ofi' relay 420 are connected in a locking circuit including their armatures 440 and 423 and armatures 412 and 401. Armature 438 of the switching relay 435 has connected ground to the private wiper 453. The incoming release trunk designated 3 is connected to ground over armature 411 of the release relay 410.

If it is assumed now that the calling party replaces the receiver first and that the called party holds up the connection, the following takes place: The line relay 405 deenergizes, transmitting an impulse to the vertical magnet and to the relay 430. Relay 410 will be short circuited and releases. In spite of the fact that the line relay 405 and the release relay 410 deenergize due to the calling party having replaced the receiver, the switching relay 435 will remain locked up over its own armature 440 to ground provided by armature 401 of the back-bridge relay 400. The latter relay is kept energized over the called line loop. Ground will therefore remain connected to the private wiper 453 over the armature 438 of the switching relay. How ever, ground is disconnected from the incomrelease trunk 3 by the armature 411 of the relay 410. Tracing the release trunk conductor 3 in its various connections in the connector it will be seen that, while the relay 430 is in energized position no potential is present on the release trunk conductor leading back to the preceding switches. Relay 430 received an impulse upon the deenergization of relay 405. All preceding switches release. therefore, while the connector is kept in operated position as long as the called subscriber keeps his receiver off the book. It is very essential that ground is reconnected to the release trunk conductor 3 immediately after the release of the preceding switches in order to guard the connector against seizure while the called subscriber still on the line. This is achieved by the release of the relay 430. It w'll be seen, that ground is connected to the rel ase trunk 0 when this relay deenergizes again after it has received an impulse in parallel with the vertical magnet 445. The guarding ground may be traced from closed armature 438 of the switching relay 435, armature 431 and its resting contact, make contact and armature of the ring cutoff relay, resting contact and armature 42G, release trunk 3. The connector cannot be seized as long as the release trunk remains grounded. The release of the connector, and accordingly the removal of the ground from the release trunk, takes place when the called party finally replaces the receiver. The back-bridge relay 400 dcenergizes at that time, opening the locking circuit for the ring-cut-ofi relay 420 and for the switching relay 435.

Relay 106 of the test equipment, upon operating, opens its armature 107 interrupting thereby the loop circuit extending to the connector. This action is equivalent to the calling subscriber replacing his receiver and opening thereby the circuit for the line relay 405. The called suhscribers line loop is represented by the transformer winding shown in Fig. 4, which winding is still connected across the line conductors 1 and 2. The condition that the calling subscriber replaces his receiver before the called subscriber has hung up is therefore imitated by the test equipment and the release functions of the connector provided for this condition take place now as described above.

As far as the test equipment is concerned, this will manifest itself by a short opening of the release conductor 3. Tracing the release conductor 3 through Fig. 1 to Fig. 2, it will be seen that this conductor terminates in the winding of relay 122. lVhen ground is disconnected from the release trunk 3, relay 122 will dcenergize and switch its armature 125 

